Building the Keystone XL pipeline would lead to more manmade light and noise in sparsely populated regions, which may harm natural resources, wildlife and visitors to national parks, the U.S. Interior Department said.

In San Francisco, more than 1,300 miles from the proposed route of the Keystone XL oil pipeline, an agency charged with regulating air pollution from industrial plants and home heaters says the project is a threat.

The Bay Area Air Quality Management District has joined scores of municipalities and interest groups from California to Maine that have adopted resolutions on Keystone XL or crude from Alberta’s oil sands that the pipeline is designed to carry.

In comments the agency submitted to the State Department as part of an environmental review of the project, Interior warned that TransCanada Corp., the project’s builder, isn’t adequately dealing with risks to “cultural soundscapes” and “high quality night skies.”

“The cumulative effects of the project could adversely impact the quality of the night skies and the overall photic environment,” Willie R. Taylor, director of the office of environmental policy at Interior, wrote in a letter on April 29. The State Department posted the letter on its website this week as it releases 1.2 million comments received about the project.

The agency is reviewing Keystone, which would transport bitumen from Alberta to refineries along the U.S. Gulf of Mexico, because it would cross an international border. A final report on the pipeline’s environmental impact may be issued as early as September. After that, the department will conduct a 90-day review to determine if Keystone is in the national interest, pushing a final decision to late this year or 2014.

Environmental groups oppose the pipeline, citing the contributions of Alberta oil production on climate change and the risk of oil spills along the more than 875-mile (1,408-kilometre) route from Canada to Steele City, Nebraska.

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In separate comments in April, the Environmental Protection Agency urged the State Department to analyze the costs of greenhouse-gas emissions by refining the tar sands into fuel. Greenhouse-gas emissions from refining oil sands are 17% greater than conventional crude oil, the agency said.

The Interior Department focused on the pipeline’s impact on U.S. national parks and other public lands managed by the agency, and the comments underscore the level of scrutiny the project is getting as part of the review.

In addition to the impacts of light and noise, the department said it “has concerns with the proposed pipeline’s stream and wetland crossings,” especially those near parks.

To curb interference from noise and light, TransCanada should employ “mitigation measures such as shielded, full- cutoff lighting, timers, and motion sensitive switches,” and use “the minimum amount of illumination” for tasks along the pipeline,” according to the comments.

The Interior Department’s comments faulted the environmental review’s recommendation for noise near pump stations to meet the level common in communities rather than for a park environment “where many people go to get away from the clamour of everyday life.”

In addition, “we recommend further information and analysis of the cumulative effects of noise on visitors and natural resources be conducted,” it said.